When an adult Hercules beetle (or any insect) emerges from its pupal skin it is very soft for a period of time. During this period--between "eclosion" (emergence from pupa) and "sclerotization" (hardening of the exoskeleton)--while the insect is soft, it is said to be in a "teneral" state. Hercules beetles tend to be dark brown during this period, then exhibit their normal colors upon sclerotization. Pictured below are comparisons between teneral and sclerotized adult hercules beetles.

Teneral and sclerotized adult female hercules beetles. The females at the bottom and top are teneral, the one in the middle is sclerotized. Photo
by B. Wallin, University of Kentucky, 2003

Here, the sclerotized female is on the left and the other two are teneral. Photo
by B. Wallin, University of Kentucky, 2003

The sclerotized female is on the right and the other two are teneral. Photo
by B. Wallin, University of Kentucky, 2003

This photo also shows some size variation among adult female Hercules beetles. Photo
by B. Wallin, University of Kentucky, 2003

Original document: 7 March 2008Last updated: 7 March 2008

Photos courtesy B.
Wallin, R. Bessin, and B. Newton, University of Kentucky
The Kentucky Critter
Files are maintained by Blake Newton, Department of Entomology, University
of Kentucky.
Contact: blaken@uky.edu